Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$35.28	5.613%	$37.2603	$37.26	$37.25	$37.30
Purchase #2	$88.44	7.227%	$94.8316	$94.83	$94.85	$94.80
Purchase #3	$78.51	12.341%	$88.1989	$88.20	$88.20	$88.20
Purchase #4	$194.70	5.727%	$205.8505	$205.85	$205.85	$205.90
Purchase #5	$221.87	7.300%	$238.0665	$238.07	$238.05	$238.10
Purchase #6	$222.34	10.557%	$245.8124	$245.81	$245.80	$245.80
Purchase #7	$59.41	5.359%	$62.5938	$62.59	$62.60	$62.60
7 purchase totals =	$900.55		$972.6140	$972.61	$972.60	$972.70